Shutter assembly for electrical devices

ABSTRACT

The present invention is directed to a shutter assembly that includes a base tandem member and an inner tandem member disposed within the base tandem member between retainer walls. The inner tandem member is configured to move within the base tandem member from a shutter closed position to a shutter open position when a base tandem key member and an inner tandem key member are simultaneously engaged by a hot plug blade and a neutral plug blade of a plug blade set. An aligning retainer assembly is coupled between the base tandem member and the inner tandem member and is configured to substantially limit both the latitudinal movement and the longitudinal movement of the inner tandem member within the base tandem member such that the inner tandem member is substantially prevented from being skewed when moving between the shutter closed position and the shutter open position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is application claims priority under 35 U.S.C. 119 (e) to U.S. Provisional Patent Application Ser. No. 61/635,432, filed on Apr. 19, 2012, the content of which is relied upon and incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to electrical devices, and particularly to electrical devices having safety shutters.

2. Technical Background

Electric service is provided in a structure by installing electric circuits throughout the structure. Each electric circuit includes electrical wiring that interconnects various kinds of electrical wiring devices that are disposed at various locations throughout a structure depending on the electrical design. Most people are familiar with electrical wiring devices such as outlet receptacles, light switches, dimmers, ground fault circuit interrupters, and the like. For example, duplex outlet receptacles are typically installed in wall mounted device boxes. After they are properly terminated to the electrical wiring, a cover plate is installed over the outlet receptacle and the device wall box to “complete the enclosure” and installation. The term “completing the enclosure” means that no energized wires or electrical conductors are accessible to a user. Receptacles are not only found in electrical wiring devices but in other electrical devices as well such as appliances, raceways, multiple outlet strips, power taps and extension cords.

Receptacles are often associated with protective devices such as ground fault circuit interrupters (GFCIs), transient voltage surge suppressors (TVSS) and arc fault circuit interrupters (AFCIs) are examples of electrical protective devices because, as their name suggests, they are used to protect persons and structures from being harmed by electrical fault conditions. Protective devices are typically equipped with a set of interrupting contacts that are used to break the connection between the line terminals and load terminals when the protective device detects a fault condition. Stated differently, the line/load electrical connection is broken to interrupt the load circuit and thereby remove the fault condition.

Electrical devices have line terminals for connecting the device to a source of AC power, and load terminals for connecting the device to an electrical load (or the electrical wiring that is connected to the load). Line terminals are configured to interface with upstream wires or receptacles to provide power to the electrical device from the AC power source. There are two kinds of load terminals in electrical devices: receptacle load terminals, and feed-thru load terminals. The receptacle load terminals are contact structures that are configured to accept and pinch the blades of a plug that is inserted therebetween to provide power to the load. Feed-thru terminals, on the other hand, are configured to terminate wires which are connected to one or more electrical devices that are downstream from the electrical device. A branch electric circuit of an electrical distribution system often includes a string of downstream receptacles.

One safety issue that has been problematic for parents and other caregivers relates to the danger of shock or electrocution of young children. Toddlers and young children seem to have a propensity of inserting objects such as paper clips, screwdriver blades and other such things into the receptacle contact openings. Unfortunately, this scenario often results in an electric shock, burns, or electrocution. In one approach that has been considered, electrical receptacles are equipped with shuttered openings that prevent foreign objects that are inserted into the receptacle openings from touching the live receptacle contacts within. However, many related art designs are ineffective because these shutters often operate if the child manages to simultaneously place an object in the hot and neutral openings. What is needed is a shutter mechanism that only opens when an actual plug is being inserted into the receptacle.

In one approach that has been considered, the related art shutters are overly complex because they comprise multiple parts and spring elements that are not integrated into a unitary sub-assembly. Many of these related art shutters have a housing that includes the moving shutter components. This approach has a drawback in that the housing adds to the bulk and thickness of the shutter assembly. The cost and time of assembling the shutter mechanism make these designs unattractive. Further, automated environments often generate vibrations and mechanical forces that tend to introduce failure modes.

The shutter assemblies briefly discussed above are typically not appropriate for 15/20 A devices. Those skilled in the art will understand that in a 15 A plug blade set, the hot blade is parallel with the neutral blade. However, in a 20 A plug blade set the neutral blade is perpendicular to the hot blade. Thus, combination 15 A/20 A devices typically employ a neutral opening T-slot that accommodates both types of plug blade sets.

In yet another approach that has been considered, a shutter assembly has been considered that eliminates the shutter housing. The shutter assembly includes a lower shutter member that accommodates an upper shutter member there within. A spring is disposed between the upper and lower shutter members such that the spring force urges the shutter members apart to maintain the shutters in a closed state. For 20 A or 15 A/20 A receptacles, an additional shutter is accommodated within the lower shutter member. One drawback associated with this arrangement is that the upper shutter may become skewed within the bottom shutter. When this occurs, the shutter assembly movement between the open and closed position becomes compromised. In addition if the insertion of the plug blade is too forceful, the shutter assembly may be permanently fixed in the open state. What is needed is a shutter assembly that addresses these issues in a reliable manner. Moreover, if the shutter assembly under consideration is adapted for 15 A/20 A use, the application of a few pounds of force with, e.g., a screw driver, may be enough to drive a shutter protecting the T-slot opening into the open position.

What is needed is a shutter assembly that addresses the drawbacks and reliability issues described above. Moreover, a shutter assembly is needed that is suitable for 15 A, 15/20 A or 20 A use. A 15/20 A shutter assembly is needed that maintains the shutters in a closed position even when excessive force is applied to them.

SUMMARY OF THE INVENTION

The present invention addresses the needs described above by providing a shutter assembly that addresses the drawbacks outlined above. Moreover, the present invention provides a shutter assembly that is suitable for 15/20 A use. A 15/20 A shutter assembly of the present invention prevents access to the neutral receptacle contacts even when excessive force is being applied to the shutter mechanism.

One aspect of the present invention is directed to a shutter assembly for use in an electrical device. The electrical device includes a housing assembly having at least one set of receptacle openings configured to receive a plug blade set. The plug blade set includes a hot plug blade and a neutral plug blade. The assembly includes a base tandem member having a major base surface disposed between retainer walls, the major base surface including a hot contact aperture and a neutral contact aperture configured to accommodate the hot plug blade and the neutral plug blade, respectively. The base tandem member further includes a base tandem key member. An inner tandem member is disposed within the base tandem member and between the retainer walls, the inner tandem member including an inner tandem key member. The inner tandem member is configured to move within the base tandem member from a shutter closed position to a shutter open position when the base tandem key member and the inner tandem key member are simultaneously engaged by the hot plug blade and the neutral plug blade of the plug blade set. An aligning retainer assembly is coupled between the base tandem member and the inner tandem member. The aligning retainer assembly is configured to substantially limit both the latitudinal movement and the longitudinal movement of the inner tandem member within the base tandem member such that the inner tandem member is substantially prevented from being skewed when moving between the shutter closed position and the shutter open position.

In another aspect, the present invention is directed to a shutter assembly for use in an electrical device. The electrical device includes a housing assembly having at least one set of receptacle openings configured to receive a plug blade set. The plug blade set includes a hot plug blade and a neutral plug blade. The assembly includes a base tandem member including a major base surface disposed between retainer walls, the major base surface including a hot contact aperture and a neutral contact aperture configured to accommodate the hot plug blade and the neutral plug blade, respectively. The base tandem member further includes a base tandem key member. An inner tandem member is disposed within the base tandem member and between the retainer walls. The inner tandem member includes an inner tandem key member. A third tandem member is coupled to the base tandem member and the inner tandem member. The third tandem member is configured to block a foreign object from accessing the neutral receptacle opening of the at least one set of receptacle openings in the shutter closed position. The inner tandem member and the third tandem member are configured to move within the base tandem member from a shutter closed position to a shutter open position when the base tandem key member and one of the inner tandem key member, or inner tandem key member in combination with the third tandem member, are simultaneously engaged by the hot plug blade and the neutral plug blade of the plug blade set, respectively. An aligning retainer assembly is coupled between the base tandem member, the inner tandem member, and the third tandem member. The aligning retainer assembly is configured to substantially limit a three-dimensional movement of the inner tandem member or the third tandem member within the base tandem member such that the inner tandem member or third tandem member are substantially prevented from being skewed.

Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a shutter assembly in accordance with an embodiment of the present invention;

FIG. 2 is an isometric view of the shutter assembly depicted in FIG. 1 shown from a different viewing angle;

FIG. 3 is an isometric view of a bottom tandem component of the shutter assembly depicted in FIG. 1;

FIG. 4 is an isometric view of an inner tandem component of the shutter assembly depicted in FIG. 1;

FIG. 5 is an isometric view of a third tandem component of the shutter assembly depicted in FIG. 1;

FIG. 6 is a detail isometric view of the inner tandem member in combination with the third tandem component;

FIG. 7 is a detail isometric view of the bottom tandem member in combination with the third tandem component;

FIG. 8 is an isometric view of a protective device incorporating the shutter assembly depicted in FIG. 1;

FIG. 9 is a detail view of the protective device depicted in FIG. 8 with the front cover removed; and

FIG. 10 is a detail view of the shutter assembly of FIG. 1 disposed within a separator member of the protective device depicted in FIG. 8;

FIG. 11 is an isometric detail view of the protective device depicted in FIG. 8 with the housing removed;

FIG. 12 is an isometric view of another electrical wiring device incorporating the shutter assembly depicted in FIG. 1;

FIG. 13 is a detail view of the electrical wiring device depicted in FIG. 12 with the front cover removed;

FIG. 14 is a detail view of the shutter assembly of FIG. 1 disposed within a separator member of the protective device depicted in FIG. 12;

FIG. 15 is an isometric detail view of the electrical wiring device depicted in FIG. 12 with the housing removed;

FIG. 16 is an isometric view of another protective device incorporating the shutter assembly depicted in FIG. 1; and

FIG. 17 is an isometric view of the underside of the front cover assembly of the device depicted in FIG. 16.

DETAILED DESCRIPTION

Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. An exemplary embodiment of the shutter assembly of the present invention is shown in FIG. 1, and is designated generally throughout by reference numeral 10.

As embodied herein and depicted in FIG. 1, an isometric view of a shutter assembly 10 in accordance with an embodiment of the present invention is disclosed. As shown herein, the shutter assembly is for use in an electrical wiring device that includes at least one set of receptacle openings. As shown in, e.g., FIG. 8, the electrical wiring device includes a housing assembly that has a front cover; the front cover includes receptacle openings that are configured to receive a plug blade set. The shutter assembly 10 is disposed under the front cover and prevents access to electrical power unless the hot and neutral blades of the plug blade set are simultaneously inserted into the receptacle openings. Stated differently, the shutter 10 will not open when an object is inserted into either the hot receptacle opening or the neutral receptacle opening.

The shutter assembly 10 includes a base tandem member 20 that accommodates an inner tandem member 30 there within. A spring member 50 is disposed between the base tandem 20 and the inner tandem 30 to maintain the shutter in a closed state. In a 15 A embodiment, the shutter assembly 10 only includes the aforementioned components. In a 15 A/20 A shutter assembly a third tandem member 40 is included for reasons that will become apparent below.

The base tandem member includes side retainer walls 20-1 on either side of major base surface 20-2. The major base slide surface 20-2 may be fabricated using any suitable thermoplastic resin material that has a high tensile strength, stiffness, resilience, fatigue endurance, and a very low coefficient of friction. The thermoplastic materials may comprise Polyoxymethylene (POM), polytetrafluoroethylene (Teflon), homopolymer, or copolymer materials. In one example embodiment, an acetal homopolymer material that exhibits a tensile strength of 9,000 Psi, a flexural strength of about 11,000 Psi, and a dynamic coefficient of friction in an approximate range of 0.1 to 0.3 was employed to implement the base tandem 20, the inner tandem 30 and the third tandem 40. Those skilled in the art will understand that the present invention should not be construed as being limited to this example embodiment.

This feature allows the inner tandem member 30 to more easily slide between the closed and open positions and is another feature of the present invention that inhibits shutter device malfunctions. As shown in more detail below, the major base slide surface 20-2 includes hot contact aperture 20-5, 15 A neutral contact aperture 20-6, and 20 A neutral contact aperture 20-7 (not shown in this view). The base tandem member 20 includes a hot contact ramp 20-4 and the inner tandem member 30 includes a neutral contact ramp 30-5. The ramps (20-4, 30-5) function as key elements that tend to respond to their respective plug blades but not to other inserted objects; for example, foreign objects such as hair pins, paper clips, etc. tend to harmlessly slide down the ramp. Thus, even if a child were to insert foreign objects into the hot and neutral receptacle openings at the same time, there is a high degree of likelihood that the shutter assembly will not open. If the third tandem member 40 is employed, the shutter assembly 10 can accommodate a 15 A plug or a 20 A plug.

As shown in FIG. 1, the third tandem member 40 is configured to slide on the base member end wall 20-11. The third tandem member 40 includes an interlocking arm 40-2 that engages locking ledge 20-12 when the shutter is in a closed and open position. The locking ledge prevents upward movement of third tandem member 40. If a 20 A neutral blade is inserted, it will strike the 20 A neutral contact ramp 40-1 at the same time the hot contact blade impacts the hot contact ramp 20-4 and it will move to the right while pushing the inner tandem ramp 30-5 toward the base tandem ramp 20-4 to compress the spring 50. If a 15 A neutral blade is inserted, the inner tandem ramp 30-5 will be forced by the 15 A neutral blade toward the hot contact ramp 20-4. The third tandem member 40 will stay in position to cover the 20 A neutral contact aperture 20-7. Once the hot and neutral blades of the plug are fully inserted they will ultimately make contact with the receptacle contacts of the electrical wiring device to thereby provide power to the load. When the plug blades are removed the ramps (20-4, 30-5, and 40-1) are forced back to their closed position as the spring 50 decompresses.

In each embodiment, the inner tandem member 30 is configured to move within the base tandem member 20 from a shutter closed position to a shutter open position when the hot key (i.e., ramp 20-4) and the neutral key (i.e., ramp 30-5 or ramp 40-1) are simultaneously engaged by the hot plug blade and the neutral plug blade, respectively. In another embodiment of the present invention, the ramps (20-4, 30-5, and/or 40-1) include keyed features formed on the ramp faces that are configured to respond to plug blades while tending to cause objects such as hair pins and paper clips to harmlessly slide off.

The shutter assembly 10 further includes an aligning retainer assembly 60 that is coupled between the base tandem member 20 and the inner tandem member 30. The retainer assembly 60 is configured to substantially limit both the latitudinal movement and the longitudinal movement of the inner tandem member 30 within the base tandem member 20 such that the inner tandem member is substantially prevented from being skewed when moving between the shutter closed position and the shutter open position. If the inner tandem member 30 is allowed to skew the potential exists for the inner tandem member 30 to become jammed within the base member 20. If this occurs, the shutter assembly 10 would not close when the plug is removed and the device 100 would be in need of replacement.

The aligning retainer assembly 60 includes a guide arm 30-7 that is inserted into a guide retainer 20-9. The guide arm 30-7 includes a connective portion 30-77 that connects the guide arm 30-7 to the neutral contact ramp 30-5. The connective portion slidably accommodates the base retainer wall 20-1 therebetween. The guide arm 30-7 also slides within the guide retainer 20-9 between the shutter closed position and the shutter open position. The limit of the shutter closed position is the interface formed by guide arm stop 30-76 and guide retainer 20-9. The extent to which the shutters open is established by the spacing between the plug blades. A cut-away portion 30-70 in guide 30-7 (not visible in this Figure) allows the longitudinal registration member 20-8 to move between the shutter closed position and the shutter open position. In an alternate embodiment cut-away portion 30-70 limits how far registration member 20-8 can travel and thus how far the shutters will open. This protects spring 50 from becoming unduly compressed. The aligning retainer assembly 60 further includes positioning tab aperture 20-10 (also not viewable in this Figure) which accommodates the third tandem positioning tab 40-4. When the third tandem positioning tab 40-4 is fully extended through aperture 20-10 (i.e., when the third tandem 40 is in the open position), it also is engaged by notch 20-94. Thus, the retainer assembly 60 also aligns and retains the third tandem 40 in its proper position.

The third tandem member 40 also includes an interface tab 40-5 (not shown in this Figure) which is disposed under the ramp 30-5 when the shutter 10 is fully assembled. As described above, the locking arm 40-2 is disposed under locking ledge 20-12. As such, interface tab 40-5 and locking arm 40-2 substantially prevent the third tandem 40 member from rotating around the x-axis. Further, the aligning retainer assembly 60 substantially prevents the third tandem from rotational movement around the y-axis. Thus, the third tandem member 40 can withstand a substantial amount of force without failing. In one embodiment, the amount of force is greater than 20 pounds of force.

Referring to FIG. 2, an isometric view of the shutter assembly depicted in FIG. 1 is shown from a different viewing angle. In this view the positioning tab 40-4 is shown more clearly inside the positioning tab aperture 20-10.

As embodied herein and depicted in FIG. 3, an isometric view of a base tandem component 20 of the shutter assembly 10 is disclosed. As noted above, the base tandem 20 includes a major base slider surface 20-2 disposed between retainer walls 20-1. Hot contact aperture 20-5, 15 A neutral contact aperture 20-6 and 20 A neutral contact aperture 20-7 are formed in the major base surface 20-2. As those skilled in the art will appreciate, the 15 A neutral contact aperture 20-6 and the 20 A neutral contact aperture 20-7 form a T-slot such that the shutter assembly 10 may be employed in either 15 A devices, 20 A devices or in combination 15 A/20 A devices. The hot contact ramp 20-4 includes a spring pocket 20-14 that is configured to accommodate one end of the spring 50. As also mentioned above, one end of the base tandem 20 includes a third end wall 20-11 on which the third tandem member 40 slides. The function and purpose of the locking ledge 20-12 was also described above. One or both of the retainer walls 20-1 may be configured to include the guide retainer 20-9 and the other related elements of the aligning retainer assembly 60, such as the positioning tab aperture 20-10, the guide channel 20-90, notch 20-94 and longitudinal registration member 20-8.

As embodied herein and depicted in FIG. 4, an isometric view of an inner tandem component 30 of the shutter assembly 10 is disclosed. The inner tandem 30 includes an inner tandem major surface 30-4 disposed between inner tandem side walls 30-1. The end portion of each sidewall 30-1 includes a stop member 30-2. An inner tandem hot contact aperture 30-3 is formed in the inner tandem major surface 30-4. When the shutter 10 is in the open position, the inner tandem hot contact aperture 30-3 is aligned with the base hot contact aperture 20-5 such that the hot blade of the plug blade extends there-through to engage the hot receptacle contact below. As described above, the inner tandem 30 includes a 15 A neutral contact key ramp 30-5. The ramp 30-5 is equipped with a spring retainer pocket 30-8. The retainer pocket 30-8 is configured to retain the proximal end of spring 50 (the distal end of spring 50 is disposed in base spring retainer pocket 20-14). The ramp 30-5 includes a cut-away portion (i.e., tab interface guide 30-6) that is configured to accommodate the third tandem interface tab 40-5.

A connective portion 30-77 extends from ramp 30-5 in a direction that is substantially normal to the guide arm 30-7 to thereby form retainer wall channel 30-74. The guide arm 30-7 includes a cut-away portion 30-70 and guide arm cam 30-72. As pointed out above, in one embodiment of the invention the cut-away 30-70 and the longitudinal registration member 20-8 (not shown in this view) limit the movement of the guide arm 30-7 in the open position. Similarly, the guide stop arm 30-76 and the guide retainer 20-9 (not shown in this view) limit the movement of the guide arm 30-7 in the closed position.

The guide arm cam 30-72 is configured to interface with the position tab cam 40-40 (shown in FIG. 5) and is configured to drive the third tandem 40 back into the closed position when the spring member 50 decompresses to drive the inner tandem 30 into the closed position. When a neutral blade drives either the inner tandem ramp 30-5 or the third tandem ramp 40-1 into the open position in the manner described above, the position cam 40-40 and the guide arm cam 30-72 are configured to slide past each other.

As embodied herein, and depicted in FIG. 5, an isometric view of a third tandem component 40 of the shutter assembly 10 is disclosed. The third tandem component 40 is configured to block the 20 A neutral contact aperture 20-7 of the T-slot opening in the major base surface 20-2. Alternatively, if the third tandem member 40 is not present, the other two shutters still function but for 15 A service only. As previously described, the third tandem 40 includes 20 A contact ramp 40-1. The ramp 40-1 includes a retainer channel 40-3 that is configured such that the third tandem can laterally slide on the base end wall 20-11 between the closed and open shutter positions. The interlocking arm 40-2 was also described above and is configured to engage the base tandem locking ledge 20-12. The function of the positioning tab 40-4 and its positioning cam 40-40 were also described above. Third tandem 40 also includes an inner tandem interface 40-5 that is inserted into the tab interface guide 30-6. The interface 40-5 includes an inner tandem interface cam 40-50 that engages a guide cam 30-60 (See FIG. 6) that is accessible via the interface guide 30-6.

Referring to FIG. 6, a detail isometric view of the inner tandem member 30 in combination with the third tandem component 40 is disclosed. In this view, the underside of the shutter assembly is shown (without the base member 20) to illustrate the camming action of the inner tandem interface 40-5 and the interface guide 30-6. Of interest is the interaction of the inner tandem interface cam 40-50 and the guide cam 30-60. Note that the guide cam 30-60 has an irregular surface that includes inclined surface 30-62, a steep inclined surface 30-66 and a transitional surface 30-64 therebetween.

If a 20 A plug is inserted, all three shutters are brought into motion. The neutral plug blade aligns with the neutral contact ramp 30-5 and so the inner tandem member 30 moves upwardly along direction “A.” The steeply inclined cam surface 30-66 begins to move relative to the cam 40-50 while the retainer wall 30-75 is in motion with respect to the third tandem positioning tab 40-4. The neutral plug blade also engages contact ramp 40-1 but the third tandem member 40 will not open yet due to interference between the retainer wall 30-75 and third tandem positioning tab 40-4. As the blade is inserted further, positioning tab 40-4 reaches guide arm cam 30-72 just beyond the retainer wall. Next, the less inclined cam surface 30-62 bears against cam surface 40-50 and the positioning tab cam 40-40 slides against cam 30-72 such that the inner tandem member moves to the left along line “C.” Since neutral apertures (20-6, 20-7) are both open, the neutral plug blade can be inserted into the neutral receptacle contact.

Once the 20 A plug blades are removed from the shutter assembly 10, the spring 50 establishes a return motion of the inner tandem member 30 approximately along line “B” rightwardly. This motion is guided by the cammed surfaces on the inner tandem member and the third tandem member in a controlled sequence that prevents the shutter assembly from jamming. The various cams described above limit the rotation of the third tandem member in the z-axis during this motion. Initially, the guide arm cam 30-72 is driven against position tab cam 40-40 such that the guide cam 30-60 is moves relative to the interface cam 40-50 until the inner tandem interface 40-5 is disposed inside the interface guide 30-6. At this point, the steeply inclined cam surface 30-66 is adjacent cam surface 40-55.

On the other hand, if a 15 A neutral plug blade (as part of a plug blade set) engages the ramp 30-5, the inner tandem 30 is driven upwardly along line “A” to open the 15 A neutral aperture (20-6). The third tandem 40 remains in place (neutral aperture 20-7 remains closed.) Once the plug blades are removed from the shutter assembly 10, the spring 50 drives the inner tandem member 30 downwardly along line “A” until the guide cam 30-60 abuts the tandem interface cam 40-50. The 15 A neutral aperture 20-6 (FIG. 3) is now closed.

Referring to FIG. 7, a detail isometric view of the bottom tandem member 20 in combination with the third tandem component 40 is disclosed. In this view, the underside of the shutter assembly 10 is shown (without the inner tandem member 30) to illustrate the relationship between the third tandem 40 and the 20 A neutral opening 20-7. The 15 A neutral opening, of course, is covered by the inner tandem 30 in the closed position. As explained above in reference to FIG. 1, the third tandem 40 includes a channel 40-3 that fits over the end wall 20-11 of the base tandem member. The third tandem 40 slides along line “C” to open and close the 20 A neutral opening 20-7. In particular, if a 20 A neutral plug blade (as part of a plug blade set) engages the ramp 40-1, the third tandem 40 will move to the left along line “C” and the 20 A neutral opening 20-7 will be open. Note that a small end portion of the positioning tab 40-4 extends through the positioning tab aperture 20-10 in side wall 20-1 and is visible in the view of FIG. 7. When the third tandem 40 is driven to the left, the end portion of the positioning tab 40-4 will engage the notch 20-94. When the plug blade is removed (as explained above in reference to FIG. 6), the guide arm 30-7 slides within the channel 20-90 and the guide arm cam 20-72 engages the position tab cam 40-40 (See FIG. 6) and drives the third tandem 40 along line “C” to the right.

If a foreign object such as a hair pin or the like is inserted into a receptacle opening, the shutter ramps (20-4, 30-5, or 40-1) will tend to harmlessly direct the object downwardly to the base major surface 20-2 by virtue of its sloped surface and low coefficient of friction. On the other hand, when plug blades are inserted into the receptacle apertures, the force applied by the hot plug blade and the neutral plug blade are essentially equal and the ramps (20-4 and 30-5) are forced together as described above. Thus, the ramp structures are keyed to accept the plug blades and reject other form factors. Moreover, as described below, even if the foreign object simulates a plug blade, the present invention will still prevent access to the underlying contact.

The discussion of the shutter assembly 10 operation is incomplete without reference to the self-aligning features (20-8, 20-3) described in reference to FIGS. 8-17 described below. The base tandem 20 includes a snap-in element 20-3 (FIGS. 1-3) that prevents the shutter assembly from moving in the z-direction but allows the shutter assembly to move in the longitudinal direction (i.e., along the y-axis). Moreover, the longitudinal registration member 20-8 is configured to be inserted into a corresponding gap or interruption 108-12 in the side wall of the portion of the electrical wiring device that accommodates the shutter assembly 10 (See FIG. 10). Taken together, these alignment features allow the shutter assembly to move in the longitudinal direction within the gap in the side wall. In an embodiment of the invention the longitudinal limit is effected by the end wall 108-10 of the trays 108-1 (FIG. 10) or by the side wall of the front cover of the device 100 (FIG. 16). Stated differently, the design includes deliberate longitudinal play 108-14 (FIG. 10) such that the insertion of a foreign object into a receptacle opening pushes the assembly to one longitudinal limit of play or the opposite limit of play to thereby misalign the shutters. Thus, when a first foreign object and a second foreign object are inserted into the hot and neutral receptacle apertures, respectively, even a small instantaneous time delay between the insertion of the two foreign objects will cause the shutters to misalign such that access to the underlying contacts is denied.

In another embodiment of the invention, the end walls 108-10 of tray 108-1 are configured to align the shutters with respect to the receptacle openings such that the shutter assembly has little or no play. The end wall provides additional protection from the insertion of a foreign object. Stated differently, the end wall will prevents any attempt to diagonally insert a paper clip or a similar object into a receptacle opening to by-pass the shutter assembly.

In another embodiment of the invention, the end walls 108-10 are configured to allow longitudinal play of the shutter assembly in the separator tray to facilitate assembly. Ribs in the front cover (not shown) serve to limit the play and align the shutters with respect to the receptacle openings.

It is well known that plug blades are arranged in pairs (hot and neutral). This pairing is of course a keyed arrangement. This keyed arrangement ensures that the hot blade and the neutral blade engage the shutter assembly at the same time to force the base tandem 20 and the inner tandem 30 together such that they can engage the underlying contacts. Because the shutter assembly is configured to move longitudinally in the manner described above, the shutters are also configured to be self-aligning. As described above, if a foreign object is inserted into one receptacle opening, the shutter assembly 10 will be misaligned if a set of plug blades are inserted thereafter. However, when the plug blades are inserted, one of the plug blades will engage its corresponding ramp first such that the shutter assembly 10 moves longitudinally in the opposite direction. This time, however, the shutter 10 will slide until the other ramp engages the other blade to thereby center the assembly 10 between the longitudinal limits of play. Again, this self-centering is a prerequisite for the apertures in the shutter aligning with the receptacle openings. Thus, the shutter assembly 10 is self-aligning within the electrical wiring devices of the present invention.

As embodied herein and depicted in FIG. 8, an isometric view of a protective device 100 incorporating the shutter assembly 10 is disclosed. Device 100 includes a housing assembly that includes body member 102 and front cover member 104. The front cover 104 includes a substantially square raised portion that extends through an aesthetic cover plate (not shown). The protective device 100 depicted in FIG. 8 is configured to be deployed within a modular electrical wiring system that includes a frame assembly disposed in the device wall box. The device is inserted until the snap elements 102-1 engage corresponding elements in the frame. Reference is made to U.S. Provisional Patent Application Ser. No. 61/635,432, filed on Apr. 19, 2012, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of the Modular Electrical Wiring System.

The front cover 104 includes two 15 A/20 A receptacles 106. Each receptacle 106 includes a hot plug blade opening, a T-slotted neutral plug blade opening 106-3, and ground prong opening 106-2. The T-slotted neutral opening includes, of course, a 20 A neutral plug blade opening 106-30. In this embodiment, a shutter assembly 10 is disposed under each receptacle 106.

The protective device 100 includes a test button 104-1 which is connected to a GFCI test circuit disposed within the housing. The front cover 104 also includes a reset button 104-2 that is configured to reset the interrupting contacts of the protective device 100 when they are tripped. Device 100 also includes a ground wire 102-2 which is connected to premise wiring during device installation. In an alternate embodiment the ground wire is omitted and grounding to the premise wiring accomplished by way of the frame.

Referring to FIG. 9, a detail view of the protective device 100 depicted in FIG. 8 with the front cover removed is disclosed. Device 100 includes a separator member 108 that is disposed under the front cover 104. The separator 108 positions the shutter assemblies 10 over the hot and neutral receptacle contacts in the manner shown. As shown in FIG. 9, the ground receptacle contacts 106-20 are not protected by shutters in this embodiment.

Referring to FIG. 10, a detail view of the shutter assembly 10 disposed within the separator member 108 is disclosed. The separator member 108 includes shutter assembly trays 108-1 that flank a central platform 108-2. The shutter assemblies 10 are inserted into the trays 108-1. The trays 108-1 include the central gap 108-12 that accommodates the longitudinal registration member 20-8. The “longitudinal play” 108-14 is also depicted herein. The function of these elements was described above. The central platform includes ground contact apertures 108-20 that accommodate the ground contacts 106-20. A triangular test platform 108-3 is disposed in one corner of the separator 108. The test platform includes a test pin aperture 108-30 that, of course, accommodates the test button pin 104-20 (not shown).

Referring to FIG. 11, an isometric detail view of the protective device 100 depicted in FIG. 8 with the housing removed is disclosed. In this view, the neutral receptacle contact structure 112-1 and hot receptacle contact structure 112-1 are disposed in another separator member 110 underneath the top separator member 108. (The hot receptacle contact structure 112-2 cannot be seen in this view). The separator 110 holds receptacle contact structures 112-1 and 112-2 in place and electrically isolates them. Since the separators (108, 110) are aligned with each other, it follows that the shutter assemblies 10 and the receptacle contact structures 112-1, 112-2 are aligned.

A portion of the protective circuit 200 is shown underneath the lower separator 110. In addition, the neutral side of the circuit interrupter 202 is shown in this view. The load neutral cantilever 116 is parallel to the exposed side of the printed circuit board (PCB) 200-1 and includes a cantilevered load neutral contact 202-6 disposed at the end portion thereof. A fixed receptacle load neutral contact 202-2 is an integrally formed portion of the neutral receptacle contact structure 112-1. The line neutral contact 202-4 is shown between fixed contact 202-2 and the load neutral contact 202-6 and is disposed on the end of a line neutral cantilever which is not visible in this view.

As embodied herein and depicted in FIG. 12, an isometric view of another electrical wiring device 100 incorporating the shutter assembly 10 is disclosed. This embodiment is directed to a full duplex receptacle that does not include any protective electronics. Device 100 includes a housing assembly that includes body member 102 and front cover member 104. The front cover 104 includes a substantially square raised portion that extends through an aesthetic cover plate (not shown). The electrical wiring device 100 depicted in FIG. 12 is configured to be deployed within a modular electrical wiring system that includes a frame assembly disposed in the device wall box. The device is inserted until the snap elements 102-1 engage corresponding elements in the frame. Reference is made to U.S. Provisional Patent Application Ser. No. 61/635,432, filed on Apr. 19, 2012, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of the Modular Electrical Wiring System.

The front cover 104 includes two 15 A/20 A receptacles 106. Each receptacle 106 includes a hot plug blade opening, a T-slotted neutral plug blade opening 106-3, and ground prong opening 106-2. The T-slotted neutral opening includes, of course, a 20 A neutral plug blade opening 106-30. In this embodiment, a shutter assembly 10 is disposed under each receptacle 106. Device 100 also includes a ground wire 102-2 which is connected to premise wiring during device installation. In an alternate embodiment the ground wire is omitted and grounding to the premise wiring accomplished by way of the frame.

Referring to FIG. 13, a detail view of the electrical wiring device 100 depicted in FIG. 12 with the front cover removed is disclosed. Device 100 includes a separator tray member 108 that is disposed under the front cover 104. The separator tray member 108 positions the shutter assemblies 10 over the hot and neutral receptacle contacts in the manner shown. As shown in FIG. 13, the ground receptacle contacts 106-20 are not protected by shutters in this embodiment.

Referring to FIG. 14, a detail view of the shutter assembly 10 disposed within the separator member 108 is disclosed. The separator member 108 includes shutter assembly trays 108-1 that flank a central platform 108-2. The shutter assemblies 10 are inserted into the trays 108-1. The trays 108-1 include the central gap 108-12 that accommodates the longitudinal registration member 20-8. The “longitudinal play” 108-14 is also depicted herein. The function of these elements was described above. The central platform includes ground contact apertures 108-20 that accommodate the ground contacts 106-20.

Referring to FIG. 15, an isometric detail view of the electrical wiring device 100 depicted in FIG. 12 with the housing removed is disclosed. In this view, the neutral receptacle contact structure 106-30 and hot receptacle contact structure 106-10 are shown underneath the separator tray member 108. The body member 102 (which is not shown in this view) holds the receptacle contact structures 106-10 and 106-30 in place and electrically isolates them.

As shown in FIG. 16, an isometric view of another protective device 100 incorporating the shutter assembly depicted in FIG. 1 is shown. In this embodiment, a conventional protective device 100 is depicted. The term conventional means a protective device 100 that is directly mounted to the device box using ground strap 107. As before, however, the protective device 100 includes receptacles 106 at either end thereof. A shutter assembly 10 is disposed under each receptacle 106 to provide protection against shock or electrocution. The protective circuit disposed in device 100 may be configured to detect a ground fault, an arc fault, or both. This is also true of the device depicted in FIGS. 8-11. Moreover, the shutter assemblies may be coupled to a wiring state detection circuit that is configured to lock the shutter assemblies in the closed position until the wiring state detection circuit detects that the line terminals 100-1 are properly connected to a source of AC power. Reference is made to U.S. Pat. No. 8,044,299, and U.S. patent application Ser. No. 12/987,648 which are incorporated herein by reference as though fully set forth in their entirety, for a more detailed explanation of a protective device with a wiring state detection circuit and locking shutters.

In reference to FIG. 17, the underside of the front cover assembly 104 of the electrical wiring device depicted in FIG. 16 is shown. In this embodiment, the shutter assembly 10 snaps into a rectangular region 104-8 formed in the underside of cover 104. The rectangular region includes the gap 104-12 that allows the longitudinal registration member 20-8 to move longitudinally in the manner described above. The top side of the shutter assembly is configured, of course, to face the receptacle openings.

As noted herein, the invention is directed to any suitable electrical device that has at least one receptacle. Non-limiting examples include appliance frames, narrow bodied raceways, and various types of outlet strips, power taps, or extension cords.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening.

The recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein.

All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not impose a limitation on the scope of the invention unless otherwise claimed.

No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. There is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

What is claimed is:
 1. A shutter assembly for use in an electrical device, the electrical device including a housing assembly having at least one set of receptacle openings configured to receive a plug blade set, the plug blade set including a hot plug blade and a neutral plug blade, the assembly comprising: a base tandem member including a major base surface disposed between retainer walls, the major base surface including a hot contact aperture and a neutral contact aperture configured to accommodate the hot plug blade and the neutral plug blade, respectively, the base tandem member further including a base tandem key member; an inner tandem member disposed within the base tandem member and between the retainer walls, the inner tandem member including an inner tandem key member, the inner tandem member being configured to move within the base tandem member from a shutter closed position to a shutter open position when the base tandem key member and the inner tandem key member are simultaneously engaged by the hot plug blade and the neutral plug blade of the plug blade set; and an aligning retainer assembly coupled between the base tandem member and the inner tandem member, the aligning retainer assembly being configured to substantially limit both the latitudinal movement and the longitudinal movement of the inner tandem member within the base tandem member such that the inner tandem member is substantially prevented from being skewed when moving between the shutter closed position and the shutter open position.
 2. The assembly of claim 1, wherein the electrical device includes a separator tray, the shutter assembly being disposed within the separator tray.
 3. The assembly of claim 1, wherein the electrical device includes a front cover, the shutter assembly being disposed within a portion of the front cover.
 4. The assembly of claim 1, wherein the plug blade set is in a 15 A or 20 A configuration.
 5. The assembly of claim 1, further comprising a spring coupled between the base tandem member and the inner tandem member, the spring being configured to drive the shutter assembly from the shutter open position to the shutter closed position.
 6. The assembly of claim 1, wherein the housing assembly includes a front cover member and wherein the shutter assembly is configure to be disposed within the front cover member adjacent the at least one set of receptacle openings.
 7. The assembly of claim 1, wherein the housing assembly includes a separator member configured to accommodate the shutter assembly, the shutter assembly being disposed adjacent the at least one set of receptacle openings.
 8. The assembly of claim 1, further comprising a third tandem member coupled to the base tandem member, the third tandem member being configured to block a foreign object from accessing a T-slot neutral receptacle contact in the shutter closed position.
 9. The assembly of claim 8, wherein the third tandem member includes a dual-cam arrangement configured to engage the inner tandem member and the aligning retainer assembly when the inner tandem member moves between the shutter open position and the shutter closed position.
 10. The assembly of claim 1, wherein the base tandem member, the inner tandem member or the third tandem member are formed of a material having a coefficient of friction that is approximately less than or equal to 0.3.
 11. The assembly of claim 10, wherein the material is selected from a group of thermoplastic material including Teflon, Polyoxymethylene (POM), homopolymer, or copolymer materials.
 12. The assembly of claim 1, wherein the electrical device is selected from a group of devices that include an electrical receptacle wiring device, a protective electrical wiring device, an appliance frame, a narrow bodied raceway device, an outlet strip, a power tap, or an extension cord.
 13. The assembly of claim 12, wherein the protective electrical wiring device includes a ground fault circuit interrupter (GFCI), a transient voltage surge suppressor (TVSS) or an arc fault circuit interrupter (AFCI).
 14. The assembly of claim 1, further comprising a third tandem member that includes a pair of tabs each having cammed surfaces that sequentially bear against corresponding cammed surfaces of the inner tandem member when the third tandem member moves from the shutter open position to the shutter closed position.
 15. The assembly of claim 14, wherein one of the corresponding cammed surfaces is disposed at an end of an arm that is exterior to one of the retainer walls.
 16. The assembly of claim 14, wherein one of the corresponding cammed surfaces includes an irregular surface.
 17. The assembly of claim 14, wherein the pair of tabs are substantially normal to each other.
 18. The assembly of claim 1, wherein the aligning retainer assembly includes at least one guide retainer structure coupled to at least one of the retainer walls of the base tandem member, the aligning retainer assembly also including at least one lateral guide arm extending from a side portion of the inner tandem member to form a first channel configured to accommodate a corresponding one of the retainer walls when the at least one lateral guide arm is inserted into the at least one guide retainer structure.
 19. The assembly of claim 18, wherein the at least one guide retainer structure includes a first stop edge that limits the longitudinal movement of the at least one lateral guide arm when the inner tandem member moves within the base tandem member from the shutter open position to the shutter closed position.
 20. The assembly of claim 18, wherein the at least one lateral guide arm includes a guide stop feature configured to limit the longitudinal movement of the at least one lateral guide arm when the inner tandem member is moving from the shutter closed position to the shutter open position.
 21. The assembly of claim 18, wherein the first channel includes a bridge member connecting the at least one lateral guide arm to the inner tandem member, the bridge member being configured to slidably move along a top portion of the base member retainer wall when the inner tandem member moves between the shutter closed position and the shutter open position.
 22. The assembly of claim 18, wherein a portion of the retainer wall is slidably enclosed on three sides when the inner tandem member moves between the shutter closed position and the shutter open position.
 23. The assembly of claim 21, wherein the portion of the retainer wall is slidably enclosed between the bridge member, the at least one lateral guide arm, and a portion of the inner tandem member.
 24. The assembly of claim 21, wherein the bridge member is substantially normal to the at least one lateral guide arm.
 25. The assembly of claim 1, further comprising a third tandem member including: a keyed third tandem structure configured to engage a 20 A neutral plug blade of the plug blade set, the keyed structure including a third tandem channel configured to slidably move along an end wall portion of the base tandem member; an interface tab configured to drive the inner tandem member from the shutter open position to the shutter closed position when the keyed structure is engaged by the 20 A neutral plug blade; a positioning tab disposed inboard of the end wall portion and configured to engage a portion of the aligning retainer assembly via a retainer wall channel; and an interlocking arm disposed outboard of the end wall portion and configured to interlock with a locking ledge portion of the end wall, the interlocking arm and the positioning tab substantially preventing the third tandem member from being skewed.
 26. The assembly of claim 25, wherein the interlocking arm, the positioning tab and interface tab substantially prevent the third tandem member from rotational movement.
 27. The assembly of claim 25, wherein the keyed third tandem structure includes an inclined ramp structure.
 28. The assembly of claim 25, wherein the interface tab includes a cammed surface configured to drive the inner tandem member into the closed position when the 20 A neutral plug blade is withdrawn from the keyed third tandem structure.
 29. The assembly of claim 25, wherein the positioning tab and the interlocking arm are substantially parallel such that the third tandem channel, the positioning tab and the interlocking arm substantially prevent rotational movement of the third tandem member about the end wall portion of the base member.
 30. The assembly of claim 25, further comprising a spring coupled between the base tandem member and the inner tandem member, the single spring being configured to drive the shutter assembly from the shutter open position to the shutter closed position.
 31. The assembly of claim 25, wherein the aligning retainer assembly includes at least one guide retainer structure coupled to at least one of the retainer walls of the base tandem member, the aligning retainer assembly also including at least one lateral guide arm extending from a side portion of the inner tandem member to form a first channel configured to accommodate a corresponding one of the retainer walls when the at least one lateral guide arm is inserted into the at least one guide retainer structure.
 32. The assembly of claim 31, wherein the aligning retainer assembly includes a tab aperture formed in a retainer wall of the base member and a notch in the at least one guide retainer structure, the positioning tab being configured to extend through the tab aperture and engage the notch when the shutter is in the open position.
 33. The assembly of claim 31, wherein a cammed arm surface of the at least one lateral guide arm is configured to engage a cammed tab surface of the positing tab in the shutter open position to thereby drive the third tandem member from the shutter open position to the shutter closed position.
 34. A shutter assembly for use in an electrical device, the electrical device including a housing assembly having at least one set of receptacle openings configured to receive a plug blade set, the plug blade set including a hot plug blade and a neutral plug blade, the assembly comprising: a base tandem member including a major base surface disposed between retainer walls, the major base surface including a hot contact aperture and a neutral contact aperture configured to accommodate the hot plug blade and the neutral plug blade, respectively, the base tandem member further including a base tandem key member; an inner tandem member disposed within the base tandem member and between the retainer walls, the inner tandem member including an the inner tandem key member; a third tandem member coupled to the base tandem member and the inner tandem member, the third tandem member being configured to block a foreign object from accessing the neutral receptacle contact of the at least one set of receptacle contacts in the shutter closed position, the inner tandem member and the third tandem member being configured to move within the base tandem member from a shutter closed position to a shutter open position when the base tandem key member and one of the inner tandem key member, or inner tandem key member in combination with the third tandem member, are simultaneously engaged by the hot plug blade and the neutral plug blade of the plug blade set, respectively; and an aligning retainer assembly coupled between the base tandem member, the inner tandem member, and the third tandem member, the aligning retainer assembly being configured to substantially limit a three-dimensional movement of the inner tandem member or the third tandem member within the base tandem member such that the inner tandem member or third tandem member are substantially prevented from being skewed.
 35. The assembly of claim 34, wherein the aligning retainer assembly includes at least one guide retainer structure coupled to at least one of the retainer walls of the base tandem member, the aligning retainer assembly also including at least one lateral guide arm extending from a side portion of the inner tandem member to form a first channel configured to accommodate a corresponding one of the retainer walls when the at least one lateral guide arm is inserted into the at least one guide retainer structure.
 36. The assembly of claim 35, wherein the at least one guide retainer structure includes a first stop edge that limits the longitudinal movement of the at least one lateral guide arm when the inner tandem member moves within the base tandem member from the shutter open position to the shutter closed position.
 37. The assembly of claim 35, wherein the at least one lateral guide arm includes a guide stop feature configured to limit the longitudinal movement of the at least one lateral guide arm when the inner tandem member is moving from the shutter closed position to the shutter open position.
 38. The assembly of claim 35, wherein the first channel includes a bridge member connecting the at least one lateral guide arm to the inner tandem member, the bridge member being configured to slidably move along a top portion of the base member retainer wall when the inner tandem member moves between the shutter closed position and the shutter open position.
 39. The assembly of claim 38, wherein a portion of the retainer wall is slidably enclosed on three sides to substantially prevent lateral movement when the inner tandem member moves between the shutter closed position and the shutter open position.
 40. The assembly of claim 38, wherein the portion of the retainer wall is slidably enclosed between the bridge member, the at least one lateral guide arm, and a portion of the inner tandem member.
 41. The assembly of claim 38, wherein the bridge member is substantially normal to the at least one lateral guide arm. 